Re: [CFT] bsdinstall and zfsboot enhancements

On 11/11/13 14:30, Teske, Devin wrote:
> (disabling default gpg-signing until they fix a bug with the quoting)
>
> On Nov 11, 2013, at 11:46 AM, Michael Dexter wrote:
>
>> Hello all,
>>
>> I have been experimenting with various BSD and GNU/Linux boot media
>> under bhyve and noticed that we may want to accommodate the "LiveCD"
>> mode of the installer, which in turn requires the correct console.
>>
>> Currently, one is prompted for VT100 for installation but this does not
>> appear to work/stick for LiveCD mode.
>>
>> Can anyone verify this?
>>
> Sorry, I mistook your issue in the previous e-mail to be on-going with the
> thread it was inline with.
>
> "LiveCD" changes things a bit.
>
> (thinks)
>
> I would expect that a prompt could do:
>
> 	1. modify /etc/ttys on the boot media
> 	2. run "init q"
>
> But there's a couple of assumptions...
>
> 	3. Can we even write to /etc/ttys?
> 	NB: We can write to /tmp because it's an md0 swap device
>
> So do we have to get fancy with slipping a unionfs layer backed by another
> md swap device above the root?
>
> That would make every file on the boot media writable (writes would go to
> the swap-backed md device and if you execute "rm -fW file" you can get back
> files that have been previously unlinked -- unlinks are stored as whiteouts in
> the swap backed md device). For all intents and purposes, the read-only file-
> system becomes writable and we could then munge /etc/ttys to enable serial
> only when a menu item is chosen.
>
> If I'm off-base, let me know... sounds like a lot of trouble.
>
> The alternative being that you enable serial by default but then I have to tell
> field engineers to unplug barcode readers before they do an install??? (that's
> a question, it may be entirely safe, but I've never tried, seems unsafe)
>
> Question is, how would you disable it? Goes back to writable filesystem.

This is why I don't think we want to modify /etc/ttys. Instead we want 
to have init do the right thing (follow the boot console) with a single 
unchanged /etc/ttys.
-Nathan